Maybe its like a "reverse" Avatar type thing, having a same species copy of something would be alot easier then having an Avatar of an alien species, so maybe the RDA had Dormant clones of a few high up people, like coffeecup, that sat in somesort of suspended state and occasionally had memory "data" uploaded from thier active counterpart ready to be automatically decanted if thier counterpart died, Pandora is isolated so a sudden death of someone in a leadership position would be "bad" for the RDA and something that could easily have happened war or not. Either way I'm sure JC is going to bring us on an incredible ride, and the Na'vi will prevail, Hell Yea!!! Come on 2020

What? Why would Jim say his back for all 4... spoilers?
So now when his on screen who cares what happens, he will be around all the way through, there goes any dramatic tension. A good writer can figure a way out of anything so i am not fussed about his return, good for him his a great character but give him more depth Jim.

If Quaritch is back, then maybe his body was found and either he got cloned or a medical miracle saved his life. Wainfleet, he was crushed, or if we believe the deleted scene, the Thanator and Neytiri killed him.

please enlighten me as to how one would have an 'immunity' from two arrows in the chest, from the badass Neytiri?!

There was a Marine that survived an RPG that got lodged right in his torso, so I figure maybe the Col. got lucky enough to survive and perhaps had an immunity from the poision on those arrowheads.

Wainfleet's suit was crushed, heavily implied he was killed by it, but you know how it goes, unless you see them actually dead, they are not dead. heck even then they aresomtimes not dead lol. it's sci fi after all.